Dutch police on Thursday arrested the father of a family kept for nearly a decade in a farmhouse, saying they were investigating whether a "certain belief in faith" was behind the case.

The 67-year-old was suspected of depriving people of their liberty, harming the health of others and money laundering following the discovery of the people in the northern village of Ruinerwold, police said.

He is the second person to be arrested. The 58-year-old tenant of the farmhouse, an Austrian man, appeared before an examining judge on Thursday on similar charges and was ordered to be detained for two weeks.

"We are dealing with an exceptional situation in this case. These people may have lived with each other in the home since 2010, apart from society," police said in a statement.

Police said the group "claim to form a family" with the suspect arrested on Thursday as the father and the six young people -- including one who raised the alarm after fleeing to a local pub -- supposedly being his children.

"We have reason to believe that the six people involved did not stay at the premises out of free will. We are investigating whether following a certain belief in life or faith has led to the living situation in which the people were found," the police statement said.

"The situation encountered requires a careful approach whereby attention and care is given to the young adults found."

The family were discovered when the oldest son walked into a local bar in a confused state and raised concerns about the welfare of the others.

Three other people who say they are the children of the 67-year-old man said they had left the family eight years ago, and had since heard no news of the others, in a statement reported by ANP news agency on Thursday.

'End of time'

Dutch media have said the family was "waiting for the end of time" as part of a doomsday cult.

Dutch police suspect that "a certain belief in life or faith" might be why six young people could have remained at this secluded farmhouse since 2010
Dutch police suspect that "a certain belief in life or faith" might be why six young people could have remained at this secluded farmhouse since 2010 ANP / Vincent Jannink

Local television station RTV Drenthe earlier said the Austrian man, identified only as Josef B, the father and the captive family were all part of South Korea's controversial Unification Church, dubbed "Moonies" after their late founder Sun Myung Moon.

Wim Koetsier of the Universal Peace Federation, the name the church now goes by, confirmed that the father of the family was a member in the 1980s, before leaving for Germany where "we lost sight of him".

He said he believed the father "together with someone else" had since started their own group.

Josef B. however "was never a member," Koetsier told ANP.

The brother of Josef B. separately said that the suspect had previously been in a cult after leaving military service, although he did not say which religious group.

"He was in a sect. We've had no contact with him for 10 years. I told him to get lost when he wanted me to become his financial guarantor," his brother Franz B. told Kronen Zeitung newspaper.

Josef B. had twin daughters with a Japanese woman, Franz B. added.

He had rented the farmhouse but did not live there, and ran a carpentry business in a nearby town.

The case has raised memories in Austria of a series of cases in which people were kept in secret rooms for years by sexual predators, including incest father Joseph Fritzl and Wolfgang Priklopil.

Priklopil's victim Natascha Kampusch told Kronen Zeitung: "It's horrible, this case has reopened all my wounds.

"But it doesn't surprise me. As we already knew, these kinds of terrible crimes don't only exist in Austria but across the world."